One known example of this type of lighting device is a so-called “LED in glass” device. An example is shown in FIG. 1. Typically a glass plate is used, with a transparent conductive coating (for example ITO) forming electrodes. The conductive coating is patterned in order to make the electrodes that are connected to a semiconductor LED device. The assembly is completed by laminating the glass, with the LEDs inside a thermoplastic layer (for example polyvinyl butyral, PVB).
Applications of this type of device are shelves, showcases, facades, office partitions, wall cladding, and decorative lighting. The lighting device can be used for illumination of other objects, for display of an image, or simply for decorative purposes.
One problem with this type of device is that semiconductor LEDs are in approximation point sources. As a result, the LEDs appear as bright dots of light, which is not always preferred, and does not give uniform illumination.
Another problem with this type of device is that there is not much flexibility to provide a time-varying output, or to provide different output effects.